1. Field of the Invention
This invention relates to the use of alkaline earth metal salts of ether carboxylic acids as catalysts for the ethoxylation or propoxylation of organic compounds containing active H atoms.
2. Discussion of Related Art
Organic compounds containing active H atoms are understood to be, for example, fatty alcohols, fatty acids and amines, which are formed in the ethoxylation or propoxylation of nonionic detergents. One typical example is the reaction of a fatty alcohol generally containing 10 to 18 carbon atoms with ethylene oxide or propylene oxide in the presence of a catalyst, the fatty alcohol reacting with several molecules of ethylene oxide or propylene oxide.
Catalysts which have been used for the polyalkoxylation reaction mentioned above include, inter alia, the following compounds: calcium and strontium hydroxide, alkoxides and phenoxides as disclosed in EP-A 0 092 256; calcium alkoxides as disclosed in U.S. Pat. No. 4,396,779; barium hydroxide as disclosed in EP 0 115 083; basic magnesium compounds, for example alkoxides as disclosed in EP 0 082 569; and magnesium and calcium fatty acid salts as disclosed in EP 085 167.
The catalysts mentioned above are attended, inter alia, by the disadvantage that they are difficult to incorporate in the reaction system or are difficult to produce.
Other conventional polyalkoxylation catalysts include potassium hydroxide and sodium methylate.
A narrow range of the degree of polyalkoxylation is of particular importance for fatty alcohol polyalkoxylates, cf. JAOCS, Vol. 63 691-695 (1986) and HAPPI, 5 (1968) pp. 52, 54, 123. Accordingly, so-called "narrow-range" alkoxylates primarily have the following advantages: low pour points; relatively high smoke points; fewer mols alkoxide to acquire solubility in water; less hydrotrope for introduction into liquid detergents; a relatively faint odor due to the presence of free (unreacted) fatty alcohols; and reduction of pluming in the spray-drying of detergent slurries containing fatty alcohol polyalkoxylate surfactants.
The range or homolog distribution of fatty alcohol polyalkoxylates is critically determined by the type of catalyst used. A measure of the homolog distribution is the so-called Q value according to the following equation: EQU Q=n.multidot.p.sup.2
where n is the mean adduct number (mean degree of ethoxylation) and p is the percentage of adduct having a certain ethylene oxide (EO) degree which is predominantly formed. Accordingly, a high Q value signifies a narrow homolog distribution range.
The ether carboxylic acids on which the alkaline earth metal salts to be used in accordance with the invention are based are known compounds which are commercially available and which may be prepared, for example, in accordance with German Pat. No. 24 18 444. The alkali metal and alkaline earth salts of these ether carboxylic acids are also known per se and have been used as highfoam surfactants with skin-care properties, for example in personal hygiene preparations (Japan 86/21 199), in cosmetic and pharmaceutical formulations (German 3 521 505, Japan 82/202 391), in cleaning formulations (Japan 85/158 298, Belgium 888 761) and as tasteless surfactants in toothpastes (U.S. Pat. No. 4,130,636, GB 1,526,379) and also in upholstery shampoos (U.S. Pat. No. 3,775,952) and as surfactants in tertiary oil recovery (U.S. Pat. No. 4,582,138, U.S. Pat. No. 4,485,873 and U.S. Pat. No. 4,478,281).